Exemplary embodiments herein generally relate to vehicle steering systems, and more particularly relate to a controllable steering rack guide system and method.
Vehicle drift or pull is a phenomenon where the vehicle tends to drift to one side or a biased steering holding is required to keep the vehicle to maintain straight-line accelerating, cruising and/or braking. Vehicle drift/pull can cause unpleasant handling instability as well as human fatigue. Meanwhile, steering kickback is the steering torque variation when the vehicle is driven on a rough road. Excessive steering kickback is one of the factors known to cause poor ride comfort. While steering kickback is mainly caused by external disturbances, such as uneven road surfaces, vehicle drift/pull can be caused either externally, such as by canted road surfaces or side wind, or internally, such as by asymmetric chassis design.
To address vehicle drift/pull and kickback performance, steering systems sometimes use the application of supplemental friction. For example, mechanical frictions can be increased in a vehicle chassis's system, such as suspension strut bearing friction and steering gearbox friction. The problem with this kind of supplemental friction is that it is passive and non-controllable. Moreover, the friction amount can degrade over time and cause poor steering feel and performance.
Other approaches for dealing with vehicle drift/pull and kickback performance include applying a supplemental power assist force and/or applying a supplemental vibration in the steering system. A drawback of applying a supplemental power assist force is that it increases the reliability concern on self-steering and is generally limited in application to electronic power steering vehicles only. A drawback of applying supplemental vibration is that it is often complicated and difficult to completely tune. As a result, the supplemental vibration can result as a new source of vibration and noise in the vehicle. Still another approach is to apply supplemental controllable friction in the steering system. However, known systems that apply supplemental controllable friction apply such friction only to the steering column shaft and are often complex and expensive.